Analyte monitoring device and methods

RELATED APPLICATION

This application claims priority to U.S. provisional application No. 61/556,824, filed Nov. 7, 2011, entitled “Analyte Monitoring Device and Methods”, the disclosure of which is incorporated herein by reference in its entirety for all purposes.

BACKGROUND

The detection and/or monitoring of glucose levels or other analytes, such as lactate, oxygen, A1C, or the like, in certain individuals is vitally important to their health. For example, the monitoring of glucose is particularly important to individuals with diabetes. Diabetics generally monitor glucose levels to determine if their glucose levels are being maintained within a clinically safe range, and may also use this information to determine if and/or when insulin is needed to reduce glucose levels in their bodies or when additional glucose is needed to raise the level of glucose in their bodies.

Growing clinical data demonstrates a strong correlation between the frequency of glucose monitoring and glycemic control. Despite such correlation, many individuals diagnosed with a diabetic condition do not monitor their glucose levels as frequently as they should due to a combination of factors including convenience, testing discretion, pain associated with glucose testing, and/or cost.

Devices have been developed for the automatic or continuous monitoring of analyte(s), such as glucose, in bodily fluid such as in the blood stream or in interstitial fluid (“ISF”), or other biological fluid. Some of these analyte measuring devices are configured so that at least a portion of the devices are positioned below a skin surface of a user, e.g., in a blood vessel or in the subcutaneous tissue of a user, so that the monitoring is accomplished in vivo.

With the continued development of analyte monitoring devices and systems, there is a need for such analyte monitoring devices, systems, and methods, as well as for processes for manufacturing analyte monitoring devices and systems that are cost effective, convenient, and with reduced pain, provide discreet monitoring to encourage frequent analyte monitoring to improve glycemic control.

SUMMARY

In view of the foregoing, devices, methods and systems for providing electronics for coupling to analyte sensors are provided including, for example, application specific integrated circuit (ASIC) configurations that provide electrical coupling with electrochemical sensors such as, for example, in vivo glucose sensors for continuous monitoring of analytes such as glucose.

These and other objects, features and advantages of the present disclosure will become more fully apparent from the following detailed description of the embodiments, the appended claims and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

<figref idref="DRAWINGS">FIG. 1</figref> shows an overall in vivo sensor based analyte monitoring system for use in certain embodiments of the present disclosure;

<figref idref="DRAWINGS">FIG. 2</figref> is an illustration of the analog front end architecture for electrical coupling to analyte sensor electrodes in an analyte monitoring system in certain embodiments of the present disclosure;

<figref idref="DRAWINGS">FIG. 3</figref> is another illustration of the analog front end architecture for electrical coupling to analyte sensor electrodes in an analyte monitoring system in certain embodiments of the present disclosure;

<figref idref="DRAWINGS">FIG. 4</figref> is yet another illustration of the analog front end architecture for electrical coupling to analyte sensor electrodes in an analyte monitoring system in certain embodiments of the present disclosure;

<figref idref="DRAWINGS">FIG. 5</figref> is yet still another illustration of the analog front end architecture for electrical coupling to analyte sensor electrodes in an analyte monitoring system in certain embodiments of the present disclosure;

<figref idref="DRAWINGS">FIG. 6</figref> is yet still a further illustration of the analog front end architecture for electrical coupling to analyte sensor electrodes in an analyte monitoring system in certain embodiments of the present disclosure; and

<figref idref="DRAWINGS">FIG. 7</figref> is yet still another illustration of the analog front end architecture for electrical coupling to analyte sensor electrodes in an analyte monitoring system in certain embodiments of the present disclosure.

DETAILED DESCRIPTION

Before the present disclosure is described in detail, it is to be understood that this disclosure is not limited to particular embodiments described, as such may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting, since the scope of the present disclosure will be limited only by the appended claims.

Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limit of that range and any other stated or intervening value in that stated range, is encompassed within the disclosure. The upper and lower limits of these smaller ranges may independently be included in the smaller ranges is also encompassed within the disclosure, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the disclosure.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Although any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present disclosure, the preferred methods and materials are now described. All publications mentioned herein are incorporated herein by reference to disclose and describe the methods and/or materials in connection with which the publications are cited.

It must be noted that as used herein and in the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise.

The publications discussed herein are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as an admission that the present disclosure is not entitled to antedate such publication by virtue of prior disclosure. Further, the dates of publication provided may be different from the actual publication dates which may need to be independently confirmed.

As will be apparent to those of skill in the art upon reading this disclosure, each of the individual embodiments described and illustrated herein has discrete components and features which may be readily separated from or combined with the features of any of the other several embodiments without departing from the scope or spirit of the present disclosure.

The figures shown herein are not necessarily drawn to scale, with some components and features being exaggerated for clarity.

<figref idref="DRAWINGS">FIG. 1</figref> shows an exemplary in vivo based analyte monitoring system <b>100</b> in accordance with embodiments of the present disclosure. As shown, in certain embodiments, analyte monitoring system <b>100</b> includes on body electronics <b>110</b> electrically coupled to in vivo analyte sensor <b>101</b> (a proximal portion of which is shown in <figref idref="DRAWINGS">FIG. 1</figref>) and attached to adhesive layer <b>140</b> for attachment on a skin surface on the body of a user. On body electronics <b>110</b> includes on body housing <b>119</b>, that defines an interior compartment. Also shown in <figref idref="DRAWINGS">FIG. 1</figref> is insertion device <b>150</b> that, when operated, transcutaneously positions a portion of analyte sensor <b>101</b> through a skin surface and in fluid contact with ISF, and positions on body electronics <b>110</b> and adhesive layer <b>140</b> on a skin surface. In certain embodiments, on body electronics <b>110</b>, analyte sensor <b>101</b>, and adhesive layer <b>140</b> are sealed within the housing of insertion device <b>150</b> before use, and in certain embodiments, adhesive layer <b>140</b> is also sealed within the housing or itself provides a terminal seal of the insertion device <b>150</b>. Devices, systems and methods that maybe used with embodiments herein are described, e.g., in U.S. patent application Ser. Nos. 12/698,124, 12/698,129 and 12/807,278, the disclosures of each of which are incorporated herein by reference for all purposes.

Referring back to the <figref idref="DRAWINGS">FIG. 1</figref>, analyte monitoring system <b>100</b> includes display device <b>120</b> which includes a display <b>122</b> to output information to the user, an input component <b>121</b> such as a button, an actuator, a touch sensitive switch, a capacitive switch, a pressure sensitive switch, a jog wheel or the like, to input data or commands to display device <b>120</b>, or otherwise control the operation of display device <b>120</b>.

In certain embodiments, input component <b>121</b> of display device <b>120</b> may include a microphone and display device <b>120</b> may include software configured to analyze audio input received from the microphone, such that functions and operation of the display device <b>120</b> may be controlled by voice commands. Display device <b>120</b> also includes data communication port <b>123</b> for wired data communication with external devices such as remote terminal (personal computer) <b>170</b>, for example. Display device <b>120</b> may also include an integrated in vitro glucose meter, including in vitro test strip port <b>124</b> to receive an in vitro glucose test strip for performing in vitro blood glucose measurements.

Referring still to <figref idref="DRAWINGS">FIG. 1</figref>, display <b>122</b> in certain embodiments is configured to display a variety of information—some or all of which may be displayed at the same or different time on display <b>122</b>. Display <b>122</b> may include, but is not limited to, graphical display <b>138</b>, numerical display <b>132</b>, trend or directional arrow display <b>131</b>, date display <b>135</b>, time of day information display <b>139</b>, battery level indicator display <b>133</b>, sensor calibration status icon display <b>134</b>, mute on/off icon display <b>136</b>, and wireless connectivity status icon display <b>137</b> that provides indication of wireless communication connection with other devices such as on body electronics <b>110</b>, data processing module <b>160</b>, and/or remote terminal <b>170</b>. As additionally shown in <figref idref="DRAWINGS">FIG. 1</figref>, display <b>122</b> may further include simulated touch screen button <b>125</b>, <b>126</b> for accessing menus, changing display graph output configurations or otherwise for controlling the operation of display device <b>120</b>.

Further details and other display embodiments can be found in, e.g., U.S. patent application Ser. Nos. 12/871,901 and 12/807,278, the disclosures of each of which are incorporated herein by reference for all purposes.

After the positioning of on body electronics <b>110</b> on the skin surface and analyte sensor <b>101</b> in vivo to establish fluid contact with ISF (or other appropriate body fluid), on body electronics <b>110</b> in certain embodiments is configured to wirelessly communicate analyte related data (such as, for example, data corresponding to monitored analyte level and/or monitored temperature data, and/or stored historical analyte related data) when on body electronics <b>110</b> receives a command or request signal from display device <b>120</b>. In certain embodiments, data from on body electronics <b>110</b> is retrieved using display device <b>120</b> or a reader device via a wireless link that operates using a near field reflective communication technique, such as is used in radio frequency identification (RFID) systems. Using such systems, in certain embodiments, analyte measurement from analyte sensor <b>101</b> can be obtained by positioning display device <b>120</b> within a short range of on body electronics <b>110</b>, and optionally actuating a button such as input component <b>121</b> to initiate data transfer from on body electronics <b>110</b> to display device <b>120</b>.

In certain embodiments, the RFID communication operates at a nominal operating frequency of 13.56 MHz, with minimum antenna input voltage for normal operation at about 2.5 Volts. Data rate for transmit and receive operations between on body electronics <b>110</b> and display device <b>120</b> may be about 20-30 kbits/second, or about 22-28 kbits/second, or about 26.48 kbits/second (data bits) in certain embodiments.

In certain embodiments, on body electronics <b>110</b> may be configured to at least periodically broadcast real time data associated with monitored analyte level which is received by display device <b>120</b> when display device <b>120</b> is within communication range of the data broadcast from on body electronics <b>110</b>, i.e., on body electronics <b>110</b> does not need a command or request from display device <b>120</b> to send information.

In certain embodiments, the received data from on body electronics <b>110</b> may be stored (permanently or temporarily) in one or more memory of the display device <b>120</b>. Referring still to <figref idref="DRAWINGS">FIG. 1</figref>, also shown in analyte monitoring system <b>100</b> are data processing module <b>160</b> and remote terminal <b>170</b>. Remote terminal <b>170</b> may include a personal computer, a server terminal, a laptop computer, or other suitable data processing devices including software for data management and analysis and communication with the components in analyte monitoring system <b>100</b>.

Data processing module <b>160</b> may include components to communicate using one or more wireless communication protocols such as, for example, but not limited to, infrared (IR) protocol, Bluetooth® protocol, Zigbee® protocol, and 802.11 wireless LAN protocol. Additional description of communication protocols including those based on Bluetooth® protocol and/or Zigbee® protocol can be found in U.S. Patent Publication No. 2006/0193375 incorporated herein by reference for all purposes.

In a further aspect, software algorithms for execution by data processing module <b>160</b> may be provided to a communication device such as a mobile telephone including, for example, WiFi or Internet enabled smart phones or personal digital assistants (PDAs) as a downloadable application for execution by the downloading communication device. Additional details describing field upgradability of software of portable electronic devices, and data processing are provided in U.S. application Ser. Nos. 12/698,124, 12/794,721, 12/699,653, and 12/699,844, and U.S. Provisional Application Nos. 61/359,265 and 61/325,155, the disclosures of each of which are incorporated by reference herein for all purposes.

<figref idref="DRAWINGS">FIG. 2</figref> is an illustration of the analog front end architecture for electrical coupling to analyte sensor electrodes in an analyte monitoring system in certain embodiments of the present disclosure. Referring to <figref idref="DRAWINGS">FIG. 2</figref>, shown is analyte sensor <b>260</b> including working electrode W, reference electrode R and counter electrode C, each of which are operatively coupled to the analog front end circuitry <b>200</b>. More specifically, referring to <figref idref="DRAWINGS">FIG. 2</figref>, working electrode W of analyte sensor <b>260</b> is electrically coupled to the input terminal of transimpedance amplifier <b>215</b>, the reference electrode R is electrically coupled to the input terminal of the servo amplifier <b>235</b>, and counter electrode C is electrically coupled to the output terminal of the servo amplifier <b>235</b>.

Referring back to <figref idref="DRAWINGS">FIG. 2</figref>, analog front end circuitry <b>200</b> is powered with a battery <b>205</b> (Vbat) that is coupled to a charge pump <b>210</b> which is configured to boost the voltage received from the battery <b>205</b> and provide the boosted voltage VChp to the other components of the analog front end circuitry <b>200</b>. For example, in certain embodiments, the battery <b>205</b> is a 1.5 Volt battery, which, when coupled to the charge pump <b>210</b>, is boosted to 3V (as output from the charge pump <b>210</b>), and thereafter, provided to the transimpedance amplifier <b>215</b>, the servo amplifier <b>235</b>, pre-amplifier <b>220</b>, the analog-to-digital converter <b>225</b>, the reference generator <b>230</b>, as well as amplifiers <b>240</b>, <b>245</b> that are configured with very high input impedance (e.g., 100 GigaOhms), to provide guard trace around the analog front end circuit connections as discussed in further detail below.

Referring again to <figref idref="DRAWINGS">FIG. 2</figref>, transimpedance amplifier <b>215</b> in certain embodiments, provides a fixed potential/voltage on the working electrode, for example, but not limited to approximately 2 volts+/−50 microVolts, and converts the current signal from the output of transimpedance amplifier <b>215</b> into a measurable voltage through resistor <b>250</b> that is part of the transimpedance amplifier <b>215</b>. Also shown in <figref idref="DRAWINGS">FIG. 2</figref> is a capacitor <b>255</b> coupled in parallel to resistor <b>250</b> for the voltage signal at the output of the transimpedance amplifier <b>215</b>. The voltage signal at the output of the transimpedance amplifier <b>215</b> is provided to the optional pre-amplifier <b>220</b> as shown in <figref idref="DRAWINGS">FIG. 2</figref>, where the pre-amplifier <b>220</b> in certain embodiments, buffers the received voltage signal and then provides the buffered voltage signal to the analog-to-digital converter <b>225</b>, which thereafter outputs the converted signal for further processing by the on body electronics <b>110</b> (<figref idref="DRAWINGS">FIG. 1</figref>). In certain embodiments, the pre-amplifier <b>220</b> has high impedance (e.g., 1 GigaOhms) that will compensate for any signal variation in the output of the transimpedance amplifier <b>215</b> which is input to the pre-amplifier <b>220</b>.

Referring still to <figref idref="DRAWINGS">FIG. 2</figref>, in certain embodiments, reference generator <b>230</b> is coupled to transimpedance amplifier <b>215</b> and servo amplifier <b>235</b>, where the reference generator <b>230</b> provides the two input voltages (2 Volts+/−50 micro Volts, and 1.96 Volts+/−20 microVolts, respectively) to the transimpedance amplifier <b>215</b> and servo amplifier <b>235</b>. Accordingly, a 40 mVolt differential is maintained between the working electrode W and the reference electrode R of the analyte sensor <b>260</b>. More specifically, the servo amplifier <b>235</b> in certain embodiments is controlled to 1.96 Volts+/−20 micro Volts, which is 40 mVolts below the 2 Volt (at which the transimpedance amplifier <b>215</b> is maintained), where the difference of 40 mVolts is the poise voltage for the analyte sensor <b>260</b> that is maintained between the working electrode W and the reference electrode R. In certain embodiments, as the analyte sensor current fluctuates, the servo amplifier <b>235</b> varies its output so that it maintains the 40 mVolts differential between the working electrode W and the reference electrode R of the analyte sensor <b>260</b>.

Referring still again to <figref idref="DRAWINGS">FIG. 2</figref>, also shown are amplifiers <b>240</b> and <b>245</b>, each receiving the boosted voltage Vchp from the charge pump <b>210</b>, and, in certain embodiments, is configured as a unity gain amplifier or a voltage follower, that is very accurate, such that they maintain zero voltage difference between the electrode connection (for example, between the reference/working electrodes and the guard trace (represented by broken circular ring around the working and reference electrode connections). More specifically, the guard traces as shown in <figref idref="DRAWINGS">FIG. 2</figref> in certain embodiments are provided to surround the entire circuit connections on the high impedance portion of the analog front end circuitry of the on body electronics <b>110</b>. Without the guard traces as shown in <figref idref="DRAWINGS">FIG. 2</figref> and described above, if there is any leakage to the circuit connections, measurement error will result, and further, in the case of leakage to the reference electrode, in certain embodiments, the silver/silver-chloride (Ag/AgCl) will degrade, effectively degrading the performance of the analyte sensor <b>260</b>.

<figref idref="DRAWINGS">FIG. 3</figref> is another illustration of the analog front end architecture <b>300</b> for electrical coupling to analyte sensor electrodes in an analyte monitoring system in certain embodiments of the present disclosure. Similar components described in conjunction with <figref idref="DRAWINGS">FIGS. 2 and 3</figref> are similarly labeled, and description of similar components in conjunction with <figref idref="DRAWINGS">FIG. 2</figref> above is applicable to the configuration provided in <figref idref="DRAWINGS">FIG. 3</figref>. Referring to <figref idref="DRAWINGS">FIG. 3</figref>, there is provided a voltage regulator <b>310</b> operatively coupled to the voltage generator <b>230</b>. Voltage regulator <b>310</b> in certain embodiments is configured to receive the boosted voltage Vchp from the charge pump <b>210</b> and provides output voltage Vhv which, as shown in <figref idref="DRAWINGS">FIG. 3</figref>, are provided to the amplifiers including transimpedance amplifier <b>215</b>, the servo amplifier <b>235</b> as well as the two unity gain amplifiers <b>240</b>, <b>245</b>. In certain embodiments, the output voltage Vhv of the voltage regulator <b>310</b> is 2.8 volts.

<figref idref="DRAWINGS">FIG. 4</figref> is yet another illustration of the analog front end architecture for electrical coupling to analyte sensor electrodes in an analyte monitoring system in certain embodiments of the present disclosure. Similar components described in conjunction with <figref idref="DRAWINGS">FIGS. 2, 3 and 4</figref> are similarly labeled, and description of similar components in conjunction with <figref idref="DRAWINGS">FIGS. 2 and 3</figref> above are applicable to the configuration provided in <figref idref="DRAWINGS">FIG. 4</figref>. Referring to <figref idref="DRAWINGS">FIG. 4</figref>, compared to the configuration shown in <figref idref="DRAWINGS">FIG. 3</figref>, there is also provided a second reference generator <b>410</b> that receives the battery voltage Vbat from battery <b>205</b> and is operatively coupled to the voltage regulator <b>310</b> as described in conjunction with <figref idref="DRAWINGS">FIG. 3</figref>.

In the manner described above, the configuration shown in <figref idref="DRAWINGS">FIG. 2</figref> provides for direct voltage measurement from the output of the transimpedance amplifier <b>215</b> to the optional pre-amplifier <b>220</b>, and thereafter processed by the analog to digital converter <b>225</b>. The configuration shown in <figref idref="DRAWINGS">FIG. 3</figref> provides for direct voltage measurement using a high voltage regulator as input to the transimpedance amplifier <b>215</b> and the servo amplifier <b>235</b>, as well as the analog to digital converter <b>225</b> and preamplifier <b>220</b>. The voltage regulator <b>310</b> receives the charge pump voltage (Vchp) and outputs the regulated voltage (Vhv). However, the regulated voltage (Vhv) output from the voltage regulator <b>310</b> shown in <figref idref="DRAWINGS">FIG. 3</figref> is not provided as input to the reference generator <b>230</b>, but rather, uses the charge pump voltage (Vchp) which is the boosted voltage from the battery <b>205</b>. Referring to <figref idref="DRAWINGS">FIG. 4</figref>, the configuration of the analog front end circuitry <b>400</b> includes a separate reference generator <b>410</b> for the voltage regulator <b>310</b> that is driven from the battery <b>205</b> voltage (Vbat).

<figref idref="DRAWINGS">FIG. 5</figref> is yet still another illustration of the analog front end architecture for electrical coupling to analyte sensor electrodes in an analyte monitoring system in certain embodiments of the present disclosure. Similar components described in conjunction with <figref idref="DRAWINGS">FIGS. 2 and 5</figref> are similarly labeled, and description of similar components in conjunction with <figref idref="DRAWINGS">FIG. 2</figref> above are applicable to the configuration provided in <figref idref="DRAWINGS">FIG. 5</figref>. Referring to <figref idref="DRAWINGS">FIG. 5</figref>, there is provided a differential amplifier with level shift <b>510</b>, which is operatively coupled between the output of the transimpendance amplifier <b>215</b> and working electrode W of the analyte sensor <b>260</b>, and the input to the analog to digital converter <b>225</b> as shown in <figref idref="DRAWINGS">FIG. 5</figref>, and is configured to provide a differential voltage measurement with a voltage shift down.

More specifically, referring to <figref idref="DRAWINGS">FIG. 5</figref>, in certain embodiments, the voltage at the working electrode W of the analyte sensor <b>260</b> is input to the differential amplifier <b>510</b> and the output voltage of the transimpedance amplifier <b>215</b>, and taking the different between the two input voltages, and thereafter, level shifting down the sensor voltage signal from the 2 Volt common mode voltage (which is the output voltage of the transimpedance amplifier <b>215</b>) to a voltage that is below 1.5 Volts. This allows the analyte sensor <b>260</b> to be driven with the battery <b>205</b> voltage (Vbat) rather than the voltage from the charge pump <b>210</b> (Vchp) resulting in a reduction in noise and power consumption, as the analog to digital converter <b>225</b> can be operated from the battery <b>205</b> voltage (Vbat) as opposed to the voltage (Vchp) from the charge pump <b>210</b>.

<figref idref="DRAWINGS">FIG. 6</figref> is yet still a further illustration of the analog front end architecture for electrical coupling to analyte sensor electrodes in an analyte monitoring system in certain embodiments of the present disclosure. Similar components described in conjunction with <figref idref="DRAWINGS">FIGS. 2 and 6</figref> are similarly labeled, and description of similar components in conjunction with <figref idref="DRAWINGS">FIG. 2</figref> above are applicable to the configuration provided in <figref idref="DRAWINGS">FIG. 6</figref>. Referring to <figref idref="DRAWINGS">FIG. 6</figref>, a current source <b>620</b> is operatively coupled to the reference generator <b>230</b> operating at the voltage Vbat from the battery <b>205</b>, and with resistor <b>610</b> operatively coupled to the working electrode W of analyte sensor <b>260</b>, the poise voltage of 40 mVolts is provided to bias the analyte sensor <b>260</b>.

As shown in <figref idref="DRAWINGS">FIG. 6</figref>, the resistor <b>610</b> is coupled between the working electrode W of the analyte sensor <b>260</b> and the input to the amplifier <b>630</b>, which, in conjunction with the field effect transistor (FET) <b>640</b> effectively operates as a current sink. More specifically, the output of the amplifier <b>630</b> is coupled to the gate terminal of the FET <b>640</b>, while the drain terminal of the FET <b>640</b> is coupled to the counter electrode C of the analyte sensor <b>260</b>, and the source terminal of the FET <b>640</b> is coupled to the pre-amplifier <b>220</b>. In this manner, in certain embodiments, the signal path from the analyte sensor <b>260</b> to the on body electronics <b>110</b> (<figref idref="DRAWINGS">FIG. 1</figref>) is sourced by the battery voltage (Vbat). Furthermore, the configuration shown in <figref idref="DRAWINGS">FIG. 6</figref> provides for less current consumption without the need for high accuracy components for sensor biasing. Additionally, as shown in <figref idref="DRAWINGS">FIG. 6</figref>, guard trace represented by dotted circles provide leakage production around the electrical connections on the analog front end circuitry <b>600</b> of the on body electronics <b>110</b> (<figref idref="DRAWINGS">FIG. 1</figref>).

More specifically, referring to <figref idref="DRAWINGS">FIG. 6</figref>, as shown, the battery <b>205</b> voltage (Vbat) drives the reference generator <b>230</b> to provide the voltage needed at the current source <b>620</b> to generate the poise voltage of 40 mVolts for biasing the sensor. As the current flows through the resistor <b>610</b>, the poise voltage is generated. As discussed above, the FET <b>640</b> and the amplifier <b>630</b> provide a current sink for the analog front end circuit <b>600</b>, which, using the charge pump voltage (Vchp) at, for example, 3 Volts, forces the reference electrode R to be maintained at 40 mVolts below the working electrode voltage (maintained at the charge pump voltage Vchp—e.g., 3 Volts). This is achieved by driving the gate terminal of the FET <b>640</b> with the output of the amplifier <b>630</b>. The sensor current, then flows through the FET <b>640</b> to the resistor <b>250</b> which is input to the pre-amplifier <b>220</b> and then to the analog to digital converter <b>225</b>.

In the manner described in conjunction with <figref idref="DRAWINGS">FIG. 6</figref>, in certain embodiments, all the components, including critical components used for sensor signal measurements, are operated with battery voltage (Vbat). By operating with the battery voltage (Vbat), the configuration shown in <figref idref="DRAWINGS">FIG. 6</figref> provides for reduced noise and power consumption compared to a configuration that operates from the charge pump voltage (Vchp). Furthermore, in the configuration shown in <figref idref="DRAWINGS">FIG. 6</figref>, the analog front end circuit and the analog to digital converter <b>225</b> are referenced to the same reference potential (i.e., ground potential), which provides for simpler calibration of the circuit components and analog to digital converter operation. Further, the configuration shown in <figref idref="DRAWINGS">FIG. 6</figref> allows for the charge pump noise to be effectively filtered because the impedance from the counter electrode C to the working electrode W is very high, so that a capacitor <b>255</b> on the counter electrode C to ground very effectively filters out the noise.

Referring still to <figref idref="DRAWINGS">FIG. 6</figref>, similar to the amplifiers <b>240</b>, <b>245</b> shown conjunction with <figref idref="DRAWINGS">FIGS. 2-5</figref>, amplifiers <b>645</b>, <b>650</b>, <b>655</b> shown in <figref idref="DRAWINGS">FIG. 6</figref> each respectively provide guard trace around the analog front end circuit connections by maintaining zero voltage difference between the electrode connections (represented by the broken circular rings). More specifically, amplifiers <b>645</b> and <b>650</b> are configured to receive the boosted voltage (Vchp) from the charge pump <b>210</b>, while amplifier <b>655</b> is configured to receive the voltage Vbat from the battery <b>205</b>, and in certain embodiments, each amplifier <b>645</b>, <b>650</b>, <b>655</b> is configured as a unity gain amplifier or a voltage follower with very high input impedance (e.g., 100 GigaOhms).

<figref idref="DRAWINGS">FIG. 7</figref> is yet still another illustration of the analog front end architecture <b>700</b> for electrical coupling to analyte sensor electrodes in an analyte monitoring system in certain embodiments of the present disclosure. Similar components described in conjunction with <figref idref="DRAWINGS">FIGS. 2 and 7</figref> are similarly labeled, and description of similar components in conjunction with <figref idref="DRAWINGS">FIG. 2</figref> above is applicable to the configuration provided in <figref idref="DRAWINGS">FIG. 7</figref>. Referring to <figref idref="DRAWINGS">FIG. 7</figref>, there is provided an unity gain amplifier <b>710</b> whose output is connected to the working electrode W of the analyte sensor <b>260</b>, and its input coupled to the reference generator <b>230</b> operating at the voltage Vbat of the battery <b>205</b>. In certain embodiments, the unity gain amplifier <b>710</b> has a 40 mVolts fixed offset voltage providing for the controlled offset voltage for biasing the sensor <b>260</b>. Also shown in <figref idref="DRAWINGS">FIG. 7</figref> are guard traces represented by the dotted circles, but as shown, and for example, compared to the configuration shown in <figref idref="DRAWINGS">FIG. 6</figref>, guard trace around the working electrode W is not needed, effectively reducing the number of guard traces to two rather than three, around each of the three electrodes of the analyte sensor <b>260</b>. More specifically, as can be seen from <figref idref="DRAWINGS">FIG. 7</figref>, in certain embodiments, amplifiers <b>720</b>, <b>730</b> with very high input impedance (e.g., 100 GigaOhms) provide guard trace around the analog front end circuit connections. Amplifier <b>720</b> receives the boosted voltage Vchp from the charge pump <b>210</b>. while amplifier <b>730</b> receives the voltage Vbat from the battery <b>205</b>, and each amplifier <b>720</b>, <b>730</b> is configured, in certain embodiments as a unity gain amplifier or a voltage follower that is very accurate, such that they maintain zero voltage difference between the electrode connections (for example, the connections for the reference electrode R and the counter electrode C.

In the manner described, in accordance with certain embodiments of the present disclosure, analog front end circuitry configurations are provided to electrically couple to the electrodes of the analyte sensor, and to process the detected sensor signals for further processing. As described above, in certain embodiments, application specific integrated circuits are designed to incorporate the analog front end circuitry to interface with the analyte sensor and also, for subsequent processing of the signals obtained from the analyte sensor for filtering, storage, and/or communication to remote locations or devices such as display device <b>120</b> (<figref idref="DRAWINGS">FIG. 1</figref>) in the analyte monitoring system <b>100</b>.

Certain embodiments of the present disclosure include an analyte monitoring device comprising an analyte sensor having a plurality of sensor electrodes, the analyte sensor having at least a portion in fluid contact with interstitial fluid under a skin layer, and sensor electronics coupled to the sensor electrodes of the analyte sensor and in signal communication with the analyte sensor, the sensor electronics including analog front end circuitry and programmed, or including programmable logic, to process signals generated by the analyte sensor and received by the analog front end circuitry, the signals generated by the analyte sensor corresponding to a monitored analyte level in the interstitial fluid, wherein the analog front end circuitry of the sensor electronics includes a single offset for calibration of the sensor electronics, and further wherein the analog front end circuitry of the sensor electronics are referenced to a reference potential.

In certain aspects, the analog front end circuitry may be provided with a fixed voltage between a working electrode and a reference electrode of the sensor to reference the analog front end circuitry of the sensor electronics to the reference potential.

In certain aspects, the fixed voltage may include the poise voltage associated with the analyte sensor.

In certain aspects, the fixed voltage may include 40 mV.

In certain aspects, the analyte sensor and the sensor electronics may be included within an integrated housing.

In certain aspects, the integrated housing may be configured to be worn on a skin surface of a patient.

In certain aspects, the analyte sensor may be configured to operate for a period of at least 7 days.

In certain aspects, the analyte sensor may be configured to operate for a period of at least 14 days.

In certain aspects, the sensor electronics may include a data communication component to communicate the processed signals to a remote device.

In certain aspects, the data communication component may include a radio frequency (RF) data communication component.

Certain embodiments include an antenna coupled to the data communication component.

In certain aspects, the antenna may include a loop antenna.

Certain embodiments include a guard trace surrounding the plurality of sensor electrodes of the analyte sensor.

Certain embodiments include an analog-to-digital converter, wherein the analog-to-digital converter is referenced to the same reference potential as the analog front end circuitry of the sensor electronics.

Certain embodiments of the present disclosure include a method comprising positioning at least a portion of an analyte sensor in fluid contact with interstitial fluid under a skin layer, the analyte sensor having a plurality of sensor electrodes, coupling sensor electronics to the sensor electrodes of the analyte sensor, wherein the sensor electronics are in signal communication with the analyte sensor, the sensor electronics including analog front end circuitry, and processing, using the sensor electronics, signals generated by the analyte sensor and received by the analog front end circuitry, the signals generated by the analyte sensor corresponding to a monitored analyte level in the interstitial fluid, wherein the analog front end circuitry of the sensor electronics includes a single offset for calibration of the sensor electronics, and further wherein the analog front end circuitry of the sensor electronics are referenced to a reference potential.

In certain aspects, the analog front end circuitry may be provided with a fixed voltage between a working electrode and a reference electrode of the sensor to reference the analog front end circuitry of the sensor electronics to the reference potential.

In certain aspects, the fixed voltage may include the poise voltage associated with the analyte sensor.

In certain aspects, the fixed voltage may include 40 mV.

In certain aspects, the analyte sensor and the sensor electronics may be included within an integrated housing.

In certain aspects, the integrated housing may be configured to be worn on a skin surface of a patient.

In certain aspects, the analyte sensor may be configured to operate for a period of at least 7 days.

In certain aspects, the analyte sensor may be configured to operate for a period of at least 14 days.

In certain aspects, the sensor electronics may include a data communication component to communicate the processed signals to a remote device.

In certain aspects, the data communication component may include a radio frequency (RF) data communication component.

Certain embodiments include coupling an antenna to the data communication component.

In certain aspects, the antenna may include a loop antenna.

Certain embodiments include surrounding the plurality of sensor electrodes of the analyte sensor with a guard trace.

Certain embodiments include operatively coupling an analog-to-digital converter to the analyte front end circuitry of the sensor electronics, wherein the analog-to-digital converter is referenced to the same reference potential as the analog front end circuitry.

Various other modifications and alterations in the structure and method of operation of the embodiments of the present disclosure will be apparent to those skilled in the art without departing from the scope and spirit of the present disclosure. Although the present disclosure has been described in connection with certain embodiments, it should be understood that the present disclosure as claimed should not be unduly limited to such embodiments. It is intended that the following claims define the scope of the present disclosure and that structures and methods within the scope of these claims and their equivalents be covered thereby.